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/**
* FreeRDP: A Remote Desktop Protocol client.
* RemoteFX Codec Library - RLGR
*
* Copyright 2011 Vic Lee
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* This implementation of RLGR refers to
* [MS-RDPRFX] 3.1.8.1.7.3 RLGR1/RLGR3 Pseudocode
*/
#if defined(HAVE_CONFIG_H)
#include <config_ac.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "rfx_bitstream.h"
/* Constants used within the RLGR1/RLGR3 algorithm */
#define KPMAX (80) /* max value for kp or krp */
#define LSGR (3) /* shift count to convert kp to k */
#define UP_GR (4) /* increase in kp after a zero run in RL mode */
#define DN_GR (6) /* decrease in kp after a nonzero symbol in RL mode */
#define UQ_GR (3) /* increase in kp after nonzero symbol in GR mode */
#define DQ_GR (3) /* decrease in kp after zero symbol in GR mode */
/* Returns the least number of bits required to represent a given value */
#define GetMinBits(_val, _nbits) \
do { \
uint32 _v = _val; \
_nbits = 0; \
while (_v) \
{ \
_v >>= 1; \
_nbits++; \
} \
} while (0)
/*
* Update the passed parameter and clamp it to the range [0, KPMAX]
* Return the value of parameter right-shifted by LSGR
*/
#define UpdateParam(_param, _deltaP, _k) \
do { \
_param += _deltaP; \
if (_param > KPMAX) \
{ \
_param = KPMAX; \
} \
if (_param < 0) \
{ \
_param = 0; \
} \
_k = (_param >> LSGR); \
} while (0)
/* Returns the next coefficient (a signed int) to encode, from the input stream */
#define GetNextInput(_n) \
do { \
if (data_size > 0) \
{ \
_n = *data++; \
data_size--; \
} \
else \
{ \
_n = 0; \
} \
} while (0)
/* Emit bitPattern to the output bitstream */
#define OutputBits(_numBits, _bitPattern) rfx_bitstream_put_bits(bs, _bitPattern, _numBits)
/* Emit a bit (0 or 1), count number of times, to the output bitstream */
#define OutputBit(_count, _bit) \
do \
{ \
uint16 b = (_bit ? 0xFFFF : 0); \
int c = _count; \
for (; c > 0; c -= 16) \
{ \
rfx_bitstream_put_bits(bs, b, (c > 16 ? 16 : c)); \
} \
} while (0)
/* Converts the input value to (2 * abs(input) - sign(input)), where sign(input) = (input < 0 ? 1 : 0) and returns it */
#define Get2MagSign(_input) ((_input) >= 0 ? 2 * (_input) : -2 * (_input) - 1)
/* Outputs the Golomb/Rice encoding of a non-negative integer */
#define CodeGR(_krp, _val) \
do { \
int lkr = (_krp) >> LSGR; \
int lval = _val; \
/* unary part of GR code */ \
uint32 lvk = lval >> lkr; \
OutputBit(lvk, 1); \
OutputBit(1, 0); \
/* remainder part of GR code, if needed */ \
if (lkr) \
{ \
OutputBits(lkr, lval & ((1 << lkr) - 1)); \
} \
/* update krp, only if it is not equal to 1 */ \
if (lvk == 0) \
{ \
UpdateParam(_krp, -2, lkr); \
} \
else if (lvk > 1) \
{ \
UpdateParam(_krp, lvk, lkr); \
} \
} while (0)
int
rfx_rlgr1_encode(const sint16 *data, uint8 *buffer, int buffer_size)
{
int k;
int kp;
int krp;
int input;
int numZeros;
int runmax;
int mag;
int sign;
int processed_size;
int lmag;
int data_size;
RFX_BITSTREAM bs;
uint32 twoMs;
rfx_bitstream_attach(bs, buffer, buffer_size);
/* initialize the parameters */
k = 1;
kp = 1 << LSGR;
krp = 1 << LSGR;
/* process all the input coefficients */
data_size = 4096;
while (data_size > 0)
{
if (k)
{
/* RUN-LENGTH MODE */
/* collect the run of zeros in the input stream */
numZeros = 0;
GetNextInput(input);
while (input == 0 && data_size > 0)
{
numZeros++;
GetNextInput(input);
}
/* emit output zeros */
runmax = 1 << k;
while (numZeros >= runmax)
{
OutputBit(1, 0); /* output a zero bit */
numZeros -= runmax;
UpdateParam(kp, UP_GR, k); /* update kp, k */
runmax = 1 << k;
}
/* output a 1 to terminate runs */
OutputBit(1, 1);
/* output the remaining run length using k bits */
OutputBits(k, numZeros);
/* note: when we reach here and the last byte being encoded is 0, we still
need to output the last two bits, otherwise mstsc will crash */
/* encode the nonzero value using GR coding */
mag = (input < 0 ? -input : input); /* absolute value of input coefficient */
sign = (input < 0 ? 1 : 0); /* sign of input coefficient */
OutputBit(1, sign); /* output the sign bit */
lmag = mag ? mag - 1 : 0;
CodeGR(krp, lmag); /* output GR code for (mag - 1) */
UpdateParam(kp, -DN_GR, k);
}
else
{
/* GOLOMB-RICE MODE */
/* RLGR1 variant */
/* convert input to (2*magnitude - sign), encode using GR code */
GetNextInput(input);
twoMs = Get2MagSign(input);
CodeGR(krp, twoMs);
/* update k, kp */
/* NOTE: as of Aug 2011, the algorithm is still wrongly documented
and the update direction is reversed */
if (twoMs)
{
UpdateParam(kp, -DQ_GR, k);
}
else
{
UpdateParam(kp, UQ_GR, k);
}
}
}
processed_size = rfx_bitstream_get_processed_bytes(bs);
return processed_size;
}
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